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Lithium polymer has significant advantages over lithium-ion, including higher energy density and lower manufacturing costs. Lithium polymer is more resistant to physical damage and can handle more charge-discharge cycles before storage capacity begins to degrade. Lithium polymer technology also offers significant advantages in thermal robustness and safety.

A key difference between traditional lithium-ion batteries and Hyundai’s lithium polymer battery solution is the overall packaging of the cell – the anode, the cathode, the electrolyte, and the encasement material. Traditional lithium-ion batteries, like those found in laptops, use what’s known as the 18650 cell format. In this format, each mass-produced cell is 18 mm. in diameter and 65 mm. tall, which is a bit larger than a “AA” battery. Each of these small metal cylinders is filled with a liquid electrolyte that facilitates the movement of lithium ions across anode and cathode, creating the battery current.

Traditional lithium-ion batteries are easy to handle, withstand mild internal pressures, and have been around in various forms since 1991. That means a manufacturing infrastructure is in place, and economies of scale are reasonably high. However, they do have several disadvantages. For example, their cylindrical shape reduces packaging efficiency and they are surprisingly complicated to manufacture since they have so many small parts. These small parts make them robust to thermal fluctuations and add significant cost and weight to the overall battery system. Cell-to-cell consistency also is extremely critical in a vehicle battery package, since the pack is only as robust as its weakest cell. Traditional lithium-ion batteries have considerable cell-to-cell variation, while Hyundai’s lithium polymer batteries deliver outstanding cell-to-cell consistency.

Lithium polymer technology uses a completely different approach. Rather than using a liquid electrolyte, which requires a robust metal casing, lithium polymer batteries use a polymer gel as the electrolyte, which allows the use of a thinner and lighter aluminum-walled encasement, or pouch. Inside each lithium polymer cell, the cathode, separator, and anode are laminated together, enabling much simpler and more reliable manufacturing. This allows the battery pack to be about 20 percent smaller than a lithium-ion battery pack, making it much easier to change the cell footprint to fit the nooks and crannies of available vehicle space.

Another key engineering challenge for Hyundai Hybrid Blue Drive has been assuring maintenance-free battery operation over the vehicle’s life – at least 10 years, and 150,000 miles – in all weather conditions. Heat is the enemy of battery cycle life. Hyundai’s thermal imaging testing shows how much cooler a lithium polymer battery is compared to today’s nickel-metal hydride battery or a conventional lithium-ion battery. Consumers will notice these advantages in improved useful life and lower maintenance costs.

Remember that Volt uses LG cells pretty much identical to Sonata's, so Volt's battery pack is as durable as Sonata's.